Major tsunamis do not occur regularly, and this haphazard generation pattern is responsible for the scarcity of reliable tsunami wave data. Sophisticated electronic measuring devices have been developed and used, but the difficulties in predicting seismic events imply that most tsunami records are obtained from conventional tide gauges. These relatively crude instruments respond differently to tides, tsunamis, storm surges, etc., all of which are of interest to marine scientists. In this paper, the tide gauge response to two idealized tsunami forms is considered. These idealized forms represent a smooth transition from a quiescent surface into a sinusoidal wave, and also the arrival of a bore followed by the sinusoidal wave. The tide gauge response shows a transient response lasting for approximately one period, and then a quasi‐steady response. The amplitude and phase of the quasi‐steady response depend critically on the tide gauge geometry, while the transient response depends on the nature of the input.